Seat belt retractor

ABSTRACT

A seat belt retractor includes a seat belt, a spool, and an emergency locking mechanism for preventing the spool from rotating in a belt withdrawal direction. The emergency locking mechanism allows rotation of the spool not in operation and prevents the rotation of the spool in the belt withdrawal direction when in operation. A lock gear includes ratchet teeth on an outer periphery of the emergency locking mechanism arranged in an annular shape. The lock gear rotates with the spool when the emergency locking mechanism is not in operation and actuates the locking mechanism when the emergency locking mechanism is in operation. A vehicle sensor includes an engaging claw and detects a vehicle deceleration larger than a predetermined deceleration. The engaging claw engages with one of the ratchet teeth to prevent rotation of the lock gear in the belt withdrawal direction.

BACKGROUND

The present application relates generally to the field of a seat belt retractor, for restraining an occupant with a seat belt withdrawn from the seat belt retractor. More particularly, the present application relates to a seat belt retractor in that an end lock due to either a vehicle sensor or a vehicle sensor and a webbing sensor may occur. The seat belt retractor may include at least one emergency locking mechanism and an automatic locking mechanism. The application also relates to the technical field of a seat belt apparatus employing a seat belt retractor to restrain an occupant with a seat belt withdrawn from the seat belt retractor.

Conventionally, a seat belt apparatus installed in a vehicle (e.g, an automobile) restrains an occupant in the event of an emergency with a seat belt made of webbing to prevent the occupant from being ejected out of their seat.

SUMMARY

One embodiment of the application relates to a seat belt retractor, comprising at least one seat belt for restraining an occupant; a spool that is rotatably supported by a frame to wind up the seat belt, an emergency locking mechanism for detecting a vehicle deceleration larger than a predetermined threshold, preventing the spool from rotating in a belt withdrawal direction, the emergency locking mechanism comprising at least one locking mechanism allowing rotation of the spool when the emergency locking mechanism is not in operation and preventing the rotation of the spool in the belt withdrawal direction when the emergency locking mechanism is in operation; a lock gear comprising ratchet teeth on an outer periphery of the emergency locking mechanism and arranged in an annular shape, the lock gear rotating together with the spool when the emergency locking mechanism is not in operation and actuating the locking mechanism when the emergency locking mechanism is in operation creating a relative rotation between the lock gear and spool; and a vehicle sensor comprising an engaging claw and detecting a vehicle deceleration larger than the predetermined deceleration in the event of an emergency, the vehicle sensor actuated to engage the engaging claw with one of the ratchet teeth of the lock gear to prevent rotation of the lock gear in the belt withdrawal direction, creating a relative rotation between the spool and the lock gear, a first end lock preventive mechanism for preventing the engaging claw of the vehicle sensor from engaging with one of the ratchet teeth of the lock gear when the seat belt is fully or nearly fully wound by the spool, the first end lock preventive mechanism comprising an end lock preventive member disposed on the frame and set at a locking position where the end lock preventive member does not allow the engaging claw of the vehicle sensor to be engaged with one of the ratchet teeth of the lock gear when the seat belt is fully or nearly fully wound and is set at a non-locking position where the end lock preventive member allows the engaging claw of the vehicle sensor to be engaged with one of the ratchet teeth of the lock gear other than when the seat belt is fully or nearly fully wound; and a control element that sets the end lock preventive member at the locking position when the seat belt is fully or nearly fully wound and sets the end lock preventive member at the non-locking position when the seat belt is not fully or nearly fully wound. A seat belt retractor as claimed in claim 1, further comprising an automatic locking mechanism which is actuated when said seat belt is fully withdrawn and prevents the withdrawal of said seat belt on the way of winding said seat belt after the seat belt is fully withdrawn until a certain amount of the seat belt is wound, and a lock switching mechanism for switching an emergency locking function mode in which an emergency locking function by said emergency locking mechanism is exercised and an automatic locking function mode in which an automatic locking function by said automatic locking mechanism is exercised, wherein said control element is disposed on a control member of said lock switching mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of a seat belt apparatus comprising a seat belt retractor according to an exemplary embodiment.

FIG. 2 is a sectional view of an exemplary embodiment of the seat belt retractor.

FIG. 3 is a perspective view of an ELR-ALR switching mechanism, an end lock preventive mechanism for a vehicle sensor, and an end lock preventive mechanism for a webbing sensor of the seat belt retractor according to an exemplary embodiment.

FIGS. 4( a), 4(b) show illustrations of the behavior of the webbing sensor of the seat belt retractor according to an exemplary embodiment. FIG. 4( a) show illustration of an embodiment of the webbing sensor in its inoperative state, and FIG. 4( b) shows an illustration of an embodiment of the webbing sensor in its operative state.

FIG. 5 shows an illustration of the ELR-ALR switching mechanism, the end lock preventive mechanism for the vehicle sensor, and the end lock preventive mechanism for the webbing sensor of the seat belt retractor according to an exemplary embodiment.

FIGS. 6( a) and 6(b) show illustrations of the end lock preventive mechanism for the webbing sensor of the seat belt retractor according to an exemplary embodiment. FIG. 6( a) is cross sectional view of stoppers and FIG. 6( b) is cross sectional view of cam grooves for controlling the stoppers according to an exemplary embodiment.

FIGS. 7( a)-7(d) are illustrations of the switching action from the ELR function mode to the ALR function mode according to an exemplary embodiment.

FIGS. 8( a) and 8(b) are illustrations of another part of the switching action from the ELR function mode to the ALR function mode according to an exemplary embodiment.

FIGS. 9( a)-9(d) are illustrations of the end lock preventive mechanism for the vehicle sensor according to an exemplary embodiment.

FIGS. 10( a) and 10(b) are illustrations for showing another part of the action of the end lock preventive mechanism for the vehicle sensor.

FIGS. 11( a) and 11(b) are illustrations for showing a part of the action of the end lock preventive mechanism for the fly wheel used in this embodiment.

FIGS. 11( c) and 11(d) are illustrations for showing a part of the behavior of a pair of stoppers and cam grooves for controlling the action of the end lock preventive mechanism for the fly wheel used in this embodiment.

FIGS. 12( a) and 12(b) are illustrations for showing another part of the action of the end lock preventive mechanism for the fly wheel used in this embodiment.

FIGS. 12( c) and 12(d) are illustrations for showing another part of the behavior of the pair of stoppers and the cam grooves for controlling the action of the end lock preventive mechanism for the fly wheel used in this embodiment.

FIG. 13( a) is an illustration showing a remaining part of the action of the end lock preventive mechanism for the fly wheel of the embodiment and FIG. 13( b) is an illustration showing a remaining part of the behavior of the pair of stoppers and the cam grooves for controlling the action of the end lock preventive mechanism for the fly wheel of this embodiment.

FIG. 14 is an illustration showing stoppers of exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

According to one exemplary embodiment, a conventional seat belt apparatus includes a seat belt retractor. The seat belt retractor may be an emergency locking seat belt retractor (ELR) for preventing the withdrawal of the seat belt. The seat belt retractor may be an automatic locking seat belt retractor (ALR) that retracts when the seat belt is fully withdrawn and prevents withdrawal of the seat belt when the seat belt is wound up. The ALR actuation may be cancelled when the seat belt is fully wound up.

The seat belt retractor can be similar to the retractor disclosed in JP-A-2004-262447, which is herein incorporated by reference in its entirety, and include a U-shaped frame, a belt reel, and a shaft rotatably supported between left and right side walls of the frame to widen the seat belt. A spring mechanism attached to one of the side walls of the frame is constructed of a spiral or similar spring for winding up a seat belt. A locking pawl is a locking member that is engaged with one of the ratchet teeth formed in the frame to prevent the spool from withdrawing. A ratchet wheel actuates the locking pawl in the event of an emergency. The retractor also includes an acceleration sensing mechanism, an engaging claw, a lever (actuator) that engages one of the ratchet teeth of the lock gear in the event of the emergency to prevent withdrawal of the belt, an inertial mass rotatably supported by the lock gear, ratchet teeth attached to the frame with which the engaging claw is engaged, an internal gear ring (ring gear) that includes internal teeth, an eccentric disk that rotates with the spool and eccentrically from the center of the spool, a control ring that rotates at a speed controlled by the eccentric disk and includes external teeth that mesh with the internal teeth of the ring gear, and an ALR lever for controlling the ALR. The ALR function may be activated when the seat belt is fully withdrawn and may be cancelled when the seat belt is fully wound.

The seat belt retractor can use an ELR function when the seat belt is not fully withdrawn. In an ELR mode a vehicle sensor is activated in the event of an emergency. When a deceleration outside of predefined values is detected, the actuator may be engaged. The actuator interfaces with an engaging claw of the actuator with one of the ratchet teeth of the lock gear so as to prevent the lock gear from rotating in the belt withdrawal direction. A relative rotation is created between the spool that is about to rotate in the withdrawing direction as a result of the inertia of the occupant and the lock gear that is prevented from rotating in the withdrawal direction. The locking pawl (corresponding to the locking mechanism of the present invention) is activated by this rotation. The activated locking pawl may engage with one of the ratchet wheels formed in the frame, preventing the spool from rotating in the belt withdrawal direction. Therefore, the withdrawal of the seat belt is stopped and the forward movement of the occupant is prevented by restraint of the seat belt.

The webbing sensor may be activated when the seat belt is withdrawn faster than normal. More particularly, the lock gear rapidly rotates during rapid withdrawal of the seat belt, actuating the inertial mass. The engaging claw of the inertial mass is engaged with one of the ratchet teeth, preventing the lock gear from rotating in the withdrawal direction. Therefore, similar to the operation of the vehicle sensor mentioned above, the rotation of the spool in the withdrawal direction is locked, preventing the withdrawal of the seat belt.

When the ALR function is used to fix a child seat to a vehicle seat with the seat belt, the seat belt may be fully withdrawn. The control ring of the automatic locking mechanism (ALR mechanism) detects that the seat belt is fully withdrawn from its eccentric rotation and activates the ALR lever. Upon activating the ALR lever, the seat belt retractor may switch from the ELR mode to the ALR mode. In the ALR mode, the rotation of the spool in the belt withdrawal direction is locked by actuation of the ALR lever, preventing the seat belt from being withdrawn until the seat belt is fully wound. Once the seat belt is fully wound, the actuation of the ALR lever is cancelled returning the seat belt retractor to the ELR function mode.

When the occupant disengages the tongue from the buckle and releases the tongue the seat belt, the seat belt may be rapidly wound by the spool. The spool is biased in the belt winding direction by the spring mechanism. When the seat belt is fully wound the rotation of the spool is stopped. Accordingly, the actuator of the vehicle sensor may rotate so that the engaging claw interfaces with one of the ratchet teeth of the lock gear. The rotation of the spool in the withdrawal direction is locked (e.g., an end lock) preventing withdrawal of the seat belt again.

According to another exemplary embodiment, to prevent an end lock a seat belt retractor constructed such that a circular arc pressing portion (stopper) may be disposed on the outer periphery of a disk-like cam plate for exercising the ALR function as described in JP-A-09-150712, which is herein incorporated by reference in its entirety. The stopper moves in the rotational direction of a lock gear by the rotation of the cam plate at a reduced speed according to the rotation of the spool. The stopper is positioned between a position allowing engagement and a apposition preventing engagement. In the position allowing engagement, the stopper allows an engaging pawl of a vehicle sensor to be engaged with the ratchet teeth of the lock gear. Conversely, in the position preventing engagement the stopper prevents the engaging claw of the vehicle sensor from being engaged with the ratchet teeth of the lock gear. When the seat belt is fully or nearly fully wound by the spool, the stopper is set to the position preventing engagement.

When the seat belt is fully wound, the stopper is set to the position preventing engagement, preventing the engaging claw of the vehicle sensor from being engaged with the ratchet teeth of the lock gear. Therefore, an end lock caused by the engaging claw of the vehicle sensor can be prevented.

The stopper is disposed on the outer periphery of the cam plate and rotates together with the cam plate allowing the stopper to be positioned in a region between the ratchet teeth of the lock gear and the engaging claw of the vehicle sensor. This structure may require the cam plate to be large. The large cam plate may result in a large rotational trajectory of the outer periphery of the cam plate, requiring a large space for movement. To prevent the stopper from interfering with the engaging claw of the vehicle sensor, the distance between the engaging claw and the ratchet teeth may be larger than that of a conventional ELR.

The large distance between the engaging claw and the ratchet teeth may make the moving distance of the engaging claw between the inoperative position and the operative position large, making the vehicle sensor large.

Due to the diversification of recent vehicles, the layout of seat belt apparatuses to be installed in vehicles varies. The combination of the operation range of the cam plate and the operation range of the stopper generally depends on the layout of the seat belt apparatus. However, the stopper for preventing the engaging claw from being engaged with the ratchet teeth and the cam plate for exercising the ALR function may be composed of the same part. To adapt the seat belt retractor to various layouts of seat belt apparatuses, each part composing the stopper and the cam plate is used for each layout because the stopper and the cam plate are composed of one part. Exclusive parts for each layout may be used, increasing parts count and cost. For example, if there are nine mounting layouts of seat belt apparatuses, then at least nine exclusive parts are required. The exclusive parts may vary corresponding to the different combinations of the operation ranges of the cam plate and the operation ranges of the stopper.

The disclosed invention is made in consideration of the aforementioned circumstances. An object of the disclosed invention is to provide a seat belt retractor that can effectively prevent an end lock due to an engaging pawl of a vehicle sensor using a structure of reduced size and to provide a seat belt unit having the same.

Another object of the present invention is to provide a seat belt retractor that can be inexpensively adapted to various mounting layouts with a lower parts count.

According to an exemplary embodiment, a seat belt retractor may include at least a seat belt for restraining an occupant, a spool rotatably supported by a frame to wind up the seat belt, and an emergency locking mechanism. The emergency locking mechanism may act to prevent the spool from rotating in the withdrawal direction when a deceleration larger than normal is detected. The emergency locking mechanism may include at least a locking mechanism that may allow rotation of a spool when the emergency locking mechanism is not in operation and may prevent the rotation of a spool in the belt withdrawing direction when the emergency locking mechanism is in operation. A lock gear comprising ratchet teeth may be formed on an outer periphery of the emergency locking mechanism and may be arranged in an annular shape. The lock gear may rotate together with the spool when the emergency locking mechanism is not in operation and may actuate the locking mechanism when the emergency locking mechanism is in operation, creating a relative rotation between the lock gear and spool. A vehicle sensor including an engaging claw may detect a vehicle deceleration larger than a predetermined deceleration such as in the event of an emergency. A vehicle sensor may engage the engaging claw with one of the ratchet teeth of the lock gear to prevent rotation of the lock gear in the belt withdrawal direction, creating a relative rotation between the spool and the lock gear. A first end lock preventive mechanism may prevent the engaging claw from engaging with one of the ratchet teeth of the lock gear when the seat belt is fully or nearly fully wound. The first end lock preventive mechanism may include an end lock preventive member disposed on the frame. The end lock preventive member may be set at a locking position such that the engaging claw of the vehicle sensor may not be engage the ratchet teeth of the lock gear when the seat belt is fully or nearly fully wound. The end lock preventive member may be set at a non-locking position where the engaging claw of the vehicle sensor may engage the ratchet teeth of the lock gear other than when said seat belt is fully or nearly fully wound. Furthermore, a control element may set the end lock preventive member at the locking position when the seat belt is fully or nearly fully wound and may set the end lock preventive member at the non-locking position when the seat belt is not fully or nearly fully wound.

According to an exemplary embodiment, a seat belt retractor includes an automatic locking mechanism. The automatic locking mechanism may be actuated when the seat belt is fully withdrawn, preventing withdrawal of the seat belt until a predetermined amount of the seat belt is wound. The embodiment may further include a lock switching mechanism for switching the seat belt retractor between an emergency locking function mode and an automatic locking function mode. Furthermore, the control element may be disposed on a control member of the lock switching mechanism.

According to an exemplary embodiment, a seat belt retractor includes a lock switching mechanism. The lock switching mechanism may include a switching lever. The switching lever may be set at an emergency locking position where the emergency locking function mode may be set or an automatic locking position where the automatic locking function mode may be set. An eccentric gear may rotate when the spool rotates. A switching lever control cam member may be used for switching the setting position of the switching lever. The control member of the lock switching mechanism may include the eccentric gear and an end lock preventive member The end lock preventive member may include an end lock preventive lever set at either the locking position or the un-locking position. The control element may be an end lock preventive member control cam for switching the setting position of the end lock preventive lever.

According to an exemplary embodiment, a seat belt retractor may include a webbing sensor that is pivotally disposed on the lock gear. When a faster than normal withdrawal is detected, the webbing sensor may actuate the lock gear. When actuated, rotation of the lock gear in the belt withdrawal direction is prevented, creating a relative rotation between the spool and the lock gear. The seat belt retractor may also include a second end lock preventive mechanism for preventing the actuation of the webbing sensor when the seat belt is fully or nearly fully wound.

According to an exemplary embodiment, a seat belt retractor includes a second end lock preventive mechanism. The second end lock preventive mechanism may include an actuation preventive member controlled by the eccentric gear. Therefore, actuation of the webbing sensor may be prevented when the seat belt is fully or nearly fully wound.

According to an exemplary embodiment, a seat belt retractors second end lock preventive mechanism may include a ring member and an actuation preventive member. The actuation preventive member may be a stopper that presses the ring member in order to prevent actuation of the webbing sensor when the seat belt is fully or nearly fully wound.

According to an exemplary embodiment, a seat belt retractor may include a stopper with a stopper biasing means. Therefore, the stopper may be biased in such a direction that the stopper presses the ring member.

According to an exemplary embodiment, a seat belt unit includes at least a seat belt for restraining an occupant, a tongue slidably supported by the seat belt, a seat belt retractor, and a buckle fixed to a surface that the tongue may be detachably latched onto. The seat belt retractor may perform at least one of winding up the seat belt or withdrawal of the seat belt and may prevent withdrawal of the seat belt in the event of an emergency.

In the embodiment of the seat belt retractor having the aforementioned structure, the control element of the first end lock preventive mechanism may set the end lock preventive member at a locking position. While in the locking position, the engaging claw of the vehicle sensor may be prevented from engaging the ratchet teeth of the lock gear when the seat belt is fully or nearly fully wound. Therefore, an end lock due to the vehicle sensor when the seat belt is fully or nearly fully wound may be prevented. Furthermore, since the end lock preventive member is not required to rotate with the control member of the lock switching mechanism, the end lock preventive member requires a smaller moving space.

Additionally, the end lock preventive member is not required to pass between the ratchet teeth of the lock gear and the engaging claw of the vehicle sensor. Thus, the end lock preventive member is limited from interfering with the engaging claw. Therefore, the distance between the engaging claw and the ratchet teeth is not required to be changed as in conventional ELRs. More particularly, the seat belt retractor of the present disclosure can be compact even with the first end lock preventive mechanism.

Additionally, the distance between the engaging claw of the vehicle sensor and the ratchet teeth of the lock gear is similar to a conventional ELR or ALR without an end lock preventive mechanism. Accordingly, the distance between the engaging claws inoperative position and operative position is not required to be changed, further limiting the vehicle sensors size. Even with the end lock preventive mechanism, a conventional vehicle sensor can be used for the seat belt retractor without any change, making manufacturing of the seat belt retractor inexpensive.

Since the control member of the automatic locking mechanism may be used for controlling the end lock preventive member, an exclusive control member for the end lock preventive member is not required. Furthermore, the number of parts in the automatic locking-type seat belt retractor can be reduced even when the first end lock preventive mechanism is included.

Additionally, the end lock preventive member includes an end lock preventive lever disposed on the frame and an end lock preventive member control cam disposed on the eccentric gear. Therefore, the seat belt retractor can be flexibly and inexpensively adapted to various layouts of seat belt apparatuses using fewer parts. This may be accomplished by setting the position of the end lock preventive member control cam relative to the eccentric gear.

According to an exemplary embodiment, the lock switching mechanism may include a switching lever and an eccentric gear. The eccentric gear may further include a switching lever control cam member for switching the setting position of the switching lever. A control member of the lock switching mechanism may include the eccentric gear. The end lock preventive member may include an end lock preventive lever that may be set between the locking position and non-locking position. The control element may be composed of the end lock preventive member control cam for switching the setting position of the end lock preventive lever. Therefore, an end lock can be prevented with a simple structure.

According to an exemplary embodiment, in a seat belt retractor including a webbing sensor the second end lock preventive mechanism may prevent the actuation of the webbing sensor when the seat belt is fully or nearly fully wound. Therefore, an end lock due to either the vehicle sensor and/or the webbing sensor may be prevented. Furthermore, an end lock when the seat belt is fully or nearly fully wound may be prevented.

According to an exemplary embodiment, the second end lock preventive mechanism may include an actuation preventive member that may be controlled by rotation of the eccentric gear. Therefore, actuation of the webbing sensor when the seat belt is fully or nearly fully wound may be prevented. As a result, the actuation of the webbing sensor can be effectively prevented.

Furthermore, since the second end lock preventive mechanism includes a ring member and a stopper for preventing actuation of the webbing sensor, a conventional webbing sensor can be employed without significant design change. Therefore, the second end lock preventive mechanism can have a simple structure because all that is required is to simply press the ring member by the stopper.

According a further exemplary embodiment, a stopper may be biased in a direction pressing the ring member by a stopper biasing mechanism. Therefore, the ring member of the webbing sensor can be locked with larger force.

According to a further exemplary embodiment, the seat belt retractor of the present disclosure may be employed, preventing end locks due to a vehicle sensor and/or a webbing sensor. Operability of the seat belt is thus improved, enabling smooth and reliable use by an occupant.

Referring to FIG. 1, a seat belt unit 1 includes a seat belt retractor 3 fixed to a vehicle body near a vehicle seat 2, and a seat belt 4 that may be withdrawn from the seat belt retractor 3. A belt anchor 4 a may be fixed to a vehicle floor or a vehicle seat 2. The seat belt unit 1 may further include a deflection fitting 5 for guiding a seat belt 4, a tongue 6 slidably supported by the seat belt 4 and that may be guided by and extend from the deflection fitting 5, and a buckle 7 fixed to the vehicle floor or the vehicle seat 2 such that the tongue 6 can be inserted and detachably latched.

The seat belt retractor 3 of this embodiment includes a U-like frame 8. The U-like frame 8 includes a back wall 8 a and left and right side walls 8 b, 8 c extending from sides of the back wall 8 a perpendicular to the extending direction of the back wall 8 a as shown in FIG. 2.

A spool 9 that a seat belt 4 is wound on may be inserted through circular holes formed in side walls 8 b, 8 c of the frame 8 such that the spool 9 is rotatably disposed. The spool 9 includes a first spool section 9 a and a second spool section 9 b that may be coaxially and rotatably fitted into the left end portion of the first spool section 9 a. The first spool section 9 a includes a belt winding portion 9 a 1, a flange portion 9 a 2 formed at the right end of the belt winding portion 9 a 1, and a rotary shaft 9 a 3 extending from the flange portion 9 a 2 in the axial direction. The second spool section 9 b has a flange portion 9 b 1 and a rotary shaft 9 b 2 extending from the flange portion 9 b 1 in the axial direction.

An end portion 9 a 4 of the rotary shaft 9 a 3 may be supported by a cover 52 of a casing 10 fixed to the side wall 8 c via a bush 50 such that the rotary shaft 9 a 3 rotates with the bush 50. A lock gear 11 may be coaxially fitted to the rotary shaft 9 a 3. In this embodiment, similar to the known lock gear 11, the lock gear 11 rotates with the rotary shaft 9 a 3 when the lock gear 11 is not prevented from rotating. The rotary shaft 9 a 3 rotates relative to the lock gear 11 when the lock gear 11 is prevented from rotating. As shown in FIG. 3, the lock gear 11 includes a number of ratchet teeth 11 a formed on the outer periphery and in an annular shape. The lock gear 11 also includes a cam hole 11 b that may be formed in a side surface of the lock gear 11.

As shown in FIG. 2 and FIG. 3, a fly wheel 12 that includes a webbing sensor and is an inertia member may be oscillatably supported by the lock gear 11. In this case, the fly wheel 12 includes an inertial mass portion 12 a and a ring portion 12 b. The inertial mass portion 12 a includes a through hole 12 d such that a projecting pin 11 c formed on the lock gear 11 may be fit through, oscillatably supporting a fly wheel 12. The inertial mass portion 12 a may include an engaging claw 12 c formed on the inertial mass portion 12 a. The ring portion 12 b may be formed in an annular shape as shown in FIGS. 4( a), 4(b), and FIG. 5.

An eccentric disk 12 may be fitted and fixed to the rotary shaft 9 a 3 of the first spool section 9 a. An eccentric gear 14 may be supported on the eccentric disk 13 such that the eccentric gear 14 may rotate relative to the eccentric disk 13.

The eccentric gear 14 includes external teeth 14 a. The external teeth 14 a can mesh with internal teeth 15 a of a ring gear 15. The ring gear 15 may be formed in the casing 10 coaxially with the spool 9 and may have an outer diameter larger than that of the eccentric gear 14. The eccentric gear 14 may include a first lever operation cam 16, a second lever operation cam 17, and a third lever operation cam 18. The third lever operation cam 18 may include a control element of the present disclosure.

Shown in FIG. 3 and FIG. 4( a), a switching lever 19 may be rotatably supported on the casing 10. The switching lever 19 may include an engaging lever 20 and a disengaging lever 21. The switching lever 19 may also include a projection 22 and an engaging arm 23 extending toward the disengaging lever 21. The projection 22 may engage with either of the first or second concavities 24 a, 24 b, thereby positioning the switching lever 19.

More particularly, when the projection 22 engages the first concavity 24 a, the switching lever 19 may be held at such a position that the engaging lever 20 may contact the first lever operation cam 16. Therefore, the engaging arm 23 of the switching lever 19 may be set such that the engaging arm 23 may not be allowed to engage any of the ratchet teeth 11 a of the lock gear 11. As a result, the seat belt retractor 3 may be set at an emergency locking mode where the seat belt retractor 3 may exercise the ELR function. When the projection 22 engages the second concavity 24 b, the switching lever 19 may be placed and held such that the disengaging lever 21 may contact the second lever operation cam 17. In this case, the engaging arm 23 may be set such that the engaging arm 23 engages one of the ratchet teeth 11 a when the lock gear 11 rotates in the belt withdrawing direction. The engaging arm 23 may engage one of the ratchet teeth 11 a by rotating the lock gear 11 in the belt withdrawing direction, thereby preventing rotation of the spool 9 in the belt withdrawing direction. Accordingly, the seat belt retractor 3 may be set to the automatic locking mode where the retractor 3 exercises the ALR function of the automatic locking mechanism (ALR mechanism). The eccentric disk 13, the eccentric gear 14, the first and second lever operation cams 16, 17, and the switching lever 19 cooperate together to function as the lock switching mechanism of the present disclosure.

The eccentric disk 13, the eccentric gear 14, the ring gear 15, the first lever operation cam 16, the second lever operation cam 17, the switching lever 19, and the switching lever position control spring 24 cooperate together to function as an ELR-ALR switching mechanism 25. According to an exemplary embodiment, the structure and operation of the ELR-ALR switching mechanism 25 may be similar to the switching mechanism described in the publication JP-A-2004-262447, which is herein incorporated by reference in its entirety.

Similar to conventional webbing sensors, the fly wheel 12 may be arranged such that the engaging claw 12 c may engage any one of the ratchet teeth 26. When the seat belt retractor 3 is not in operation (e.g., the seat belt 4 is fully wound) and the seat belt 4 is withdrawn at a speed equal to or lower than a normal withdrawing speed, the fly wheel 12 may rotate with the lock gear 11. Additionally, the fly wheel 12 may be held at a position shown in FIG. 4( a) such that the engaging claw 12 c may not engage with the ratchet wheel 26. When the seat belt 4 is withdrawn at a speed exceeding the aforementioned normal withdrawing speed, the fly wheel 12 may oscillate relative to the rotation of the lock gear 11 due to the inertial delay of the inertial mass portion 12 a. The fly wheel 12 may be set at a position as shown in FIG. 4( b) such that the engaging claw 12 c may engage one of the ratchet teeth 26. Therefore, when the seat belt 4 is rapidly withdrawn, the rotation of the spool 9 in the belt withdrawing direction may be prevented as to restrict withdrawal of the seat belt 4.

Furthermore, as shown in FIG. 2 and FIG. 3 a vehicle sensor 27 may be used as a deceleration detecting mechanism and may be attached to the side wall 8 c. The vehicle sensor 27 may be a known vehicle sensor. The vehicle sensor 27 includes an inertia ball 28 that may be actuated when a large deceleration is applied to the vehicle. Furthermore, a casing 29 may be attached to the side wall 8 c to support the inertia ball 28. An actuator 30 may be pivotally mounted to the casing 29 and may be actuated by the actuation of the inertia ball 28. Additionally, a cover 31 may be attached to the casing 29. The actuator 30 may include an engaging claw 30 a. When the inertia ball 28 is not actuated, the engaging claw 30 a may be held at a position such that the engaging claw 30 a may not engage with the ratchet teeth 11 a of the lock gear 11. When the inertia ball 28 is actuated, the engaging claw 30 a may be set at a position such that the engaging claw 30 a may not engage the ratchet teeth 11 a. When the engaging claw 30 a is not engaged with any of the ratchet teeth 11 a, the lock gear 11 may be allowed to rotate in either the belt winding direction or the belt withdrawing direction. When the engaging claw 30 a engages with one of the ratchet teeth 11 a, the lock gear 11 may be prevented from rotating in the belt withdrawing direction.

A known pretensioner 32 may be disposed on the side wall 8 b. The rotary shaft 9 b 2 of the second spool section 9 b may be rotatably supported by a casing 33. The pretensioner 32 may be actuated in the event of an emergency. The operational force of the pretensioner 32 may be transmitted to the second spool section 9 b such that the spool 9 may rotate in the belt winding direction. Therefore, the seat belt 4 may be wound up at an early stage of the emergency, thereby increasing the belt tension.

A known pawl 34 may be rotatably supported by the second spool section 9 b. The pawl 34 can be engaged with one of the teeth 35 formed in the inner periphery of the opening of the side wall 8 b. When the first spool section 9 a and the lock gear 11 rotate together in the belt withdrawing direction, the pawl 34 may hold at a position such that the pawl 34 may not engage any of the teeth 35. When the first spool section 9 a rotates in the belt withdrawing direction relative to the lock gear 11, the pawl 34 may be set by a control member (not shown) at such a position that the pawl 34 may engage one of the teeth 35. When the pawl 34 is not engaged with any of the teeth 35, the second spool section 9 b may rotate in the belt winding direction or the belt withdrawing direction. When the pawl 34 is engaged with one of the teeth 35, the second spool section 9 b may not rotate in the belt withdrawing direction. The pawl 34 and the teeth 35 may work together to compose a locking mechanism of the present disclosure. The locking mechanism, the lock gear 11, and the vehicle sensor 27 cooperate to function as an emergency locking mechanism. Similar operation and control of the pawl 34 by the control member and the cam hole 11 b is known, and is not a characterizing portion of the present embodiment, thus the detailed description thereof will be omitted.

Shown in FIG. 2, a known torsion bar 36 may extend between the first and second spool sections 9 a, 9 b. The right end portion 36 a shown in FIG. 2 of the torsion bar 36 may be adapted to rotate with the first spool section 9 a. The left end portion 36 b as shown in FIG. 2 may be adapted to rotate with the second spool section 9 b.

In an emergency situation, the pawl 34 may engage one of the teeth 35 preventing the second spool section 9 b from rotating in the belt withdrawing direction. Furthermore, the first spool section 9 a may begin to rotate in the belt withdrawing direction due to the inertia of the occupant against the seat belt. In this case, the torsion bar 36 may torsionally deform to absorb impact energy applied to the occupant by the seat belt 4.

The seat belt retractor 3 of this embodiment may include an end lock preventive mechanism. The end lock preventive mechanism may prevent an end lock that may occur due to the actuator 30 of the vehicle sensor 27 or the fly wheel 12 of the webbing sensor.

As shown in FIG. 3 and FIG. 5, the end lock preventive mechanism 37 for the vehicle sensor 27 may include an end lock preventive lever 38, an end lock preventive lever position control spring 39, an eccentric ring 13, and an eccentric gear 14.

The end lock preventive lever 38 may be rotatably supported on the casing 10. The end lock preventive lever 38 may include a locking lever 40 and an unlocking lever 41. The end lock preventive lever 38 may include a projection 42 and an end lock preventive arm 43. The projection 42 may engage with at least one of first and second concavities 39 a, 39 b as curves formed in an end lock preventive lever position control spring 39, thereby positioning the end lock preventive lever 38.

When the projection 42 engages the first concavity 39 a as shown in FIG. 5, the end lock preventive lever 38 may be positioned and held such that the third lever operation cam 18 may contact the locking lever 40 and not be allowed to contact the unlocking lever 41. The end lock preventive arm 43 may be set at an end lock prevention canceling position shown by a solid line in FIG. 5 so as to set the actuator 30 of the vehicle sensor 27 to an operable state. When the projection 42 engages the second concavity 39 b, the end lock preventive lever 38 may be positioned and held such that the third lever operation cam 18 may contact the unlocking lever 41 and may not contact the locking lever 40. The end lock preventive arm 43 may be set at an end lock preventing position shown by a two-dot chain line in FIG. 5 such that the end lock preventive arm 43 may contact the actuator 30 so as to lock the actuator 30 at the inoperable position. Accordingly, the actuator 30 may be set in the inoperable state.

According to the embodiment shown in FIG. 3 and FIGS. 6( a), 6(b), the end lock preventive mechanism 44 for the fly wheel 12 includes a pair of stoppers 45, 46, a ring portion 12 b of the fly wheel 12, an eccentric ring 13, an eccentric gear 14, and a cam groove 49 formed in the casing 10. The lock preventive mechanism 44 also includes a pair of guide grooves 47, 48 that may be spaced apart from each other in a circumferential direction and by an angle of 180° so as to oppose each other and extend linearly.

The pair of stoppers 45, 46 may be formed in a similar configuration. Each stopper may include a contact portion 45 a, 46 a that may contact the inner periphery of the ring portion 12 b of the fly wheel 12. A guided portion 45 b, 46 b may be guided to move along one of the pair of guide grooves 47, 48, and a cam follower 45 c, 46 c may move along the cam groove 49.

The pair of guide grooves 47, 48 of the eccentric gear 14 may guide the stoppers 45, 46 such that the guided portions 45 b, 46 b of the stoppers 45, 46 may move in the radial direction of the eccentric gear 17.

The cam groove 49 may include a pair of small-diameter circular grooves 49 a, 49 b that may include a small circular hole 10 a in the casing 10, through which the bush 50 may pass. The pair of large-diameter circular grooves 49 c, 49 d may include circular hole 10 a that may be large. The small-diameter circular grooves 49 a, 49 b and the large-diameter circular grooves 49 c, 49 d may form a closed loop. In this case, the pair of small-diameter circular grooves 49 a, 49 b and the pair of large-diameter circular grooves 49 c, 49 d may be alternately arranged in the circumferential direction of the circular hole 10 a. The lengths in the circumferential direction of the small-diameter circular grooves 49 a, 49 b may be set to be equal to each other. Similarly, the lengths in the circumferential direction of the large-diameter circular grooves 49 c, 49 d may be set to be equal to each other and shorter than the lengths in the circumferential direction of the small-diameter circular grooves 49 a, 49 b, respectively. Furthermore, the cam groove 49 of this embodiment may be formed by an endless-type inner peripheral wall 49 e and an endless-type outer peripheral wall 49 f that extends from the side wall of the casing 10 in the axial direction of the spool 9.

The cam follower 45 c of the stopper 45 may be positioned at one end side within the large-diameter circular groove 49 c when the seat belt 4 is fully wound. In addition, the contact portion 45 a may contact the inner periphery of the ring portion 12 b to press the ring portion 12 b in the outer radial direction.

Similarly, the cam follower 46 c of the stopper 46 may be positioned at one end within the large-diameter circular groove 49 d when the seat belt 4 is fully wound. In addition, the contact portion 46 a may contact the inner periphery of the ring portion 12 b to press the ring portion 12 b in the outer radial direction.

According to an exemplary embodiment, the cam follower 45 c may be positioned within the small-diameter circular groove 49 a when the cam follower 46 c is positioned within the small-diameter circular groove 49 b. Conversely, the cam follower 45 c may be positioned within the large-diameter circular groove 49 c when the cam follower 46 c is positioned within the large-diameter circular groove 49 d. More particularly, the positions of the cam followers 45 c, 46 c may be synchronously controlled. Therefore, the contact portions 45 a, 46 a of the stoppers 45, 46 may press the inner periphery of the ring portion 12 b simultaneously. Since the inner periphery of the ring portion 12 b may be pressed by the contact portions 45 a, 46 a, the fly wheel 12 may be set in a locked state where the fly wheel 12 can not oscillate.

A known spring mechanism 51 may be attached to the casing 10. The biasing force of the spring mechanism 51 may be transmitted to the spool 9 via the bush 50, whereby the spring mechanism 51 may bias the spool 9 in the belt winding direction. By the biasing force of the spring mechanism 51, the seat belt 4 may be fully wound onto the spool 9 when the seat belt is not used.

Hereafter, respective actions of the ELR-ALR switching mechanism 25, the end lock preventive mechanism 37, and the end lock preventive mechanism 44 will be described.

FIGS. 7( a)-7(d) and FIGS. 8( a)-8(b) show exemplary embodiments of the switching actions from the ELR function mode to the ALR function mode. FIGS. 9( a)-9(d) and FIGS. 10( a) and 10(b) are illustrations for explaining the actions of the end lock preventive mechanism 37 for the vehicle sensor 27. FIGS. 11( a) and 11(b), FIGS. 12( a) and 12(b), and FIG. 13( a) are illustrations for explaining the actions of the end lock preventive mechanism 44 for the fly wheel 12. FIGS. 11( c) and 11(d), FIGS. 12( c) and 12(d), and FIG. 13( b) are illustrations for explaining respective behaviors of the pair of stoppers 45, 46 and the cam groove 49 for controlling the actions of the end lock preventive mechanism 44 for the fly wheel 12.

When the seat belt 4 is fully wound, the seat belt retractor 3 may be set by the ELR-ALR switching mechanism 25 in a state where the seat belt retractor 3 can exercise the ELR mechanism. That is, the switching lever 19 may be positioned such that the projection 22 may engage the first concavity 24 a of the switching lever position control spring 24 as shown in FIG. 7( a). When the switching lever 19 is in this position, the first lever operation cam 16 may contact the engaging lever 20 and may not contact the disengaging lever 21. Additionally, the second lever operation cam 17 may not contact either the engaging lever 20 or the disengaging lever 21.

As shown in FIG. 9( a), the end lock preventive lever 38 of the end lock preventive mechanism 37 may be positioned such that the projection 42 may engage the second concavity 39 b of the end lock preventive lever position control spring 39. When the end lock preventive lever 38 is in this position, the third lever operation cam 18 may not contact the unlocking lever 41 and may not contact the locking lever 40. Therefore, the end lock preventive arm 43 of the end lock preventive lever 38 may be set at the end lock preventing position so that the actuator 30 may be set in the inoperative state.

Furthermore, the contact portions 45 a, 46 a of the stoppers 45, 46 of the end lock preventive mechanism 44 may not press the inner periphery of the ring portion 12 b of the fly wheel 12.

As the seat belt 4 is withdrawn in this state, the eccentric gear 14 may rotate at a reduced speed in the belt winding direction. Shown in FIG. 11( c), the cam followers 45 c, 46 c of the stoppers 45, 46 may enter into the respective large-diameter circular grooves 49 c, 49 d. Then, as shown in FIG. 11( a), the respective contact portions 45 a, 46 a may press the inner periphery of the ring portion 12 b such that the fly wheel 12 may lock. In this case, oscillation may be prevented and the fly wheel 12 may enter an inoperable state.

When the seat belt 4 is further withdrawn, the pair of cam followers 45 c, 46 c may continue to rotate in the belt winding direction until they reach the end of the large-diameter circular grooves 49 c, 49 d as shown in FIG. 11( d). While the pair of cam followers 45 c, 46 c are positioned within the large-diameter circular grooves 49 c, 49 d, as shown in FIG. 11( b), the respective contact portions 45 a, 46 a continue pressing the ring portion 12 b thereby maintaining the lock of the fly wheel 12.

As the seat belt 4 is further withdrawn, the cam followers 45 c, 46 c may further rotate in the belt winding direction disengaging the large-diameter circular grooves 49 c, 49 d and engaging the small-diameter circular grooves 49 a, 49 b as shown in FIG. 12( c). Accordingly, as shown in FIG. 12( a), the respective contact portions 45 a, 46 a may move apart from the inner periphery of the ring portion 12 b such that the lock of the fly wheel 12 is cancelled. Therefore, the fly wheel 12 may oscillate and enter an operable state.

The rotational angle of the eccentric gear 14 from when the seat belt 4 is in the fully wound state to when the pair of cam followers 45 c, 46 c enter into the small-diameter circular grooves 49 a, 49 b is about 60°. Therefore, the amount of the seat belt 4 withdrawn is small. When the seat belt 4 is withdrawn a small amount from the fully wound state, the fly wheel 12 may switch from the inoperable state to the operable state. In the operable state, the fly wheel 12 can exercise the same function as a conventional webbing sensor. Accordingly, when the seat belt 4 is withdrawn at a speed higher than normal, the fly wheel 12 may be actuated and the engaging claw 12 c may engage one of the ratchet teeth 26. Therefore the lock gear 11 may be prevented from rotating in the belt withdrawal direction. Since the spool 9 rotates relative to the lock gear 11 in the belt withdrawal direction, the pawl 34 may engage one of the internal teeth 35 of the side wall 8 b, thereby preventing the second spool section 9 b from rotating in the belt withdrawal direction. As a result, withdrawal of the seat belt 4 may be prevented.

When the pair of cam followers 45 c, 46 c enter into the small-diameter circular grooves 49 a, 49 b, the third lever operation cam 18 may contact the unlocking lever 41 as shown in FIG. 9( b). Afterwards, as the seat belt 4 is further withdrawn, the third lever operation cam 18 may press the unlocking lever 41 as shown in FIG. 9( c). Therefore, the end lock preventive lever 38 may be pivotally moved so that the projection 42 may come off the second concavity 39 b of the end lock preventive lever position control spring 39 and may engage the first concavity 39 a. Thus, the end lock preventive arm 43 of the end lock preventive lever 38 may be set and held at the end lock prevention cancelling position such that the actuator 30 of the vehicle sensor 27 may be enter an operable state. Accordingly, in the event of an emergency, similar to the conventional vehicle sensor, the actuator 30 may be actuated by movement of the inertia ball 28 such that the engaging claw 30 a may engage the ratchet teeth 11 a of the lock gear 11. When the lock gear 11 rotates in the belt withdrawing direction due to withdrawal of the seat belt 4, one of the ratchet teeth 11 a may engage the engaging claw 30 a, preventing the lock gear 11 from rotating in the belt withdrawing direction. Since the spool 9 may rotate relative to the lock gear 11 in the belt withdrawing direction, the pawl 34 may engage the internal teeth 35 of the side wall 8 b, preventing the second spool section 9 b from rotating in the belt withdrawing direction. FIG. 9( c) shows the actuator 30 in the operative state.

When the first spool section 9 a rotates in the belt withdrawing direction due to the inertia of the occupant acting on the seat belt 4, the torsion bar 36 may torsionally deform similar to a known torsion bar. The torsional deformation of the torsion bar 36 may absorb impact energy applied to the occupant by the seat belt 4.

As the seat belt 4 is further withdrawn, the third lever operation cam 18 may pass through the end lock preventive lever 38 as shown in FIG. 12( b). At this point, the end lock preventive lever 38 may be held at the end lock prevention cancelling position such that the vehicle sensor 27 may remain in an operable state. As shown in FIG. 12( d), the pair of cam followers 45 c, 46 c may further rotate in the belt winding direction, moving within the small-diameter circular grooves 49 a, 49 b. Therefore, as shown in FIG. 12( b), the contact portion 45 a may be held in a state spaced from the inner periphery of the ring portion 12 b, thereby maintaining the fly wheel 12 in an operable state.

As the seat belt 4 is further withdrawn, the eccentric gear 14 rotates in the belt winding direction such that the first lever operation cam 16 moves toward the engaging lever 20 of the switching lever 19. During this, the vehicle sensor 27 and the fly wheel 12 may maintain their operable states.

Immediately before the seat belt 4 is fully withdrawn, as shown in FIG. 7( b), the first lever operation cam 16 may press the engaging lever 20. Then, as shown in FIG. 7( c), the switching lever 19 may pivotally move such that the projection 22 of the switching lever 19 may engage the second concavity 24 b of the switching lever position control spring 24. The switching lever 19 may be positioned accordingly. That is, the engaging arm 23 may engage the ratchet teeth 11 a of the lock gear 11. Accordingly, the seat belt retractor 3 may switch from the ELR function mode to the ALR function mode.

As the seat belt 4 is fully withdrawn, as shown in FIG. 7( d), one of the ratchet teeth 11 a of the lock gear 11 may engage the engaging arm 23. In this state, the vehicle sensor 27 may maintain an operable state as shown in FIG. 9( d). Additionally, the cam followers 45 c, 46 c of the stoppers 45, 46 may be positioned at an end of the small-diameter circular grooves 49 a, 49 b on the large-diameter circular grooves 49 d, 49 c as shown in FIG. 13( b). Therefore, the contact portions 45 a, 46 a may be spaced apart from the inner periphery of the ring portion 12 b as shown in FIG. 13( a). More particularly, the fly wheel 12 may maintain an operable state.

As the spool 9 rotates in the belt winding direction from a fully withdrawn state, a certain amount of the seat belt 4 may be wound onto the spool 9. When the spool 9 rotates, the lock gear 11 may also rotate in the belt winding direction. When the lock gear 11 rotates in the belt winding direction, the engaging arm 23 may not engage the ratchet teeth 11 a. Therefore, the seat belt 4 may be smoothly wound onto the spool 9. When the seat belt 4 is withdrawn after a predetermined amount of the seat belt 4 is wound, both the spool 9 and the lock gear 11 may rotate in the belt withdrawing direction, but one of the ratchet teeth 11 a of the lock gear 11 may immediately engage with the engaging arm 23. Accordingly, the spool 9 and the lock gear 11 may be prevented from rotating in the belt withdrawing direction, thereby preventing the seat belt 4 from being withdrawn. In this case, the seat belt retractor 3 may exercise the ALR function. Due to the rotation of the spool 9 in the belt winding direction, the eccentric gear 14 may rotate in the belt withdrawing direction.

When the seat belt 4 is further wound, the third lever operation cam 18 may gradually come closer to the locking lever 40 of the end lock preventive lever 38. By further winding of the seat belt 4, as shown in FIG. 10( a), the third lever operation cam 18 may contact and press the locking lever 40. As shown in FIG. 10( b), the end lock preventive lever 38 may be pivotally moved such that the projection 42 of the end lock preventive lever 38 may disengage the first concavity 39 a and may engage the second concavity 39 b. Therefore, the end lock preventive arm 43 may be set and held at the end lock preventing position such that the actuator 30 of the vehicle sensor 27 may enter an inoperable state. Since the seat belt retractor 3 is set in the ALR function mode, the withdrawal of the seat belt 4 may be prevented in the event of an emergency as mentioned above.

Shown in FIG. 8( a), as the seat belt 4 nears being fully wound the second lever operation cam 17 may contact and press the disengaging lever 21 of the switching lever 19. Then, as shown in FIG. 8( b), the switching lever 19 may be pivotally moved such that the projection 22 of the switching lever 19 may disengage the second concavity 24 b and may engage the first concavity 24 a of the switching lever position control spring 24. Therefore, the engaging arm 23 of the switching lever 19 may be set such that the engaging arm 23 may not engage the ratchet teeth 11 a of the lock gear 11. Accordingly, the seat belt retractor 3 may switch from the ALR function mode to the ELR function mode.

As the seat belt 4 is further wound, as shown in FIG. 11( d), the cam followers 45 c, 46 c of the stoppers 45, 46 may enter into the large-diameter circular grooves 49 c, 49 d from the small-diameter circular grooves 49 a, 49 b, respectively. Therefore, the contact portions 45 a, 46 a may contact the inner periphery of the ring portion 12 b and may press the inner periphery of the ring portion 12 b. As a result, the fly wheel 12 is locked and enters an inoperable state.

As the seat belt 4 is fully wound, the rotation of the spool 9 and the eccentric gear 14 may be stopped. In this state, the vehicle sensor 27 and the fly wheel 12 may be locked such that the vehicle sensor 27 and the fly wheel 12 enter their inoperable states.

According to an exemplary embodiment, when the seat belt is fully or nearly fully wound, the end lock preventive lever 38 may be controlled by the third lever operation cam 18 of the ELR-ALR switching mechanism 25. The end lock preventive lever 38 may be set at the locking position where the engaging claw 30 a of the actuator 30 may not engage with any one of the ratchet teeth 11 a of the lock gear 11. Therefore, when the seat belt is fully or nearly fully wound, an end lock due to the vehicle sensor 27 can be prevented. Since the end lock preventive lever 38 is not required to rotate with the eccentric gear 14, the end lock preventive lever 38 requires a reduced operational range. As a result, the end lock preventive lever 38 may function using a smaller moving space, allowing for a compact design.

Since the end lock preventive lever 38 is not required to pass between the ratchet teeth 11 a of the lock gear 11 and the engaging claw 30 a of the vehicle sensor 27, the end lock preventive lever 38 may be restricted from interfering with the engaging claw 30 a. Therefore, the distance between the engaging claw 30 a and the ratchet teeth 11 a is not required to be changed similar to a conventional ELR. Therefore, aforementioned seat belt retractor 3 including an end lock preventive mechanism may be of compact design.

Furthermore, the distance between the engaging claw 30 a of the vehicle sensor 27 and the ratchet teeth 11 a of the lock gear 11 may be equal to a conventional ELR or ALR without an end lock preventive mechanism. Accordingly, the moving distance of the engaging claw 30 a between the inoperative position and the operative position is not required to be changed, allowing the vehicle sensor 27 to be small. Furthermore, even with the end lock preventive mechanism 37, a conventional vehicle sensor can be used as the vehicle sensor 27 of the seat belt retractor 3 of this embodiment without any change. Therefore, manufacturing of the seat belt retractor 3 of this embodiment may be inexpensive.

Since the eccentric gear 14 of the ALR may be used for controlling the end lock preventive lever 38, an additional exclusive control member for the end lock preventive lever 38 is not required. Therefore, the parts count of the ALR can be reduced even when the end lock preventive mechanism 37 is included.

Additionally, since the third lever operation cam 18 comprising a simple shape as an end lock preventive member control cam may be disposed on the eccentric gear 14, the seat belt retractor can be flexibly and inexpensively adapted to various layouts of seat belt apparatuses 1 with fewer parts by suitably setting the position of the third lever operation cam 18 relative to the eccentric gear 14.

Furthermore, the end lock preventive mechanism 37 may be included with the eccentric gear 14. The eccentric gear 14 may further include a third lever operation cam 18 for switching the setting position of the end lock preventive lever 38. As a result, an end lock due to the vehicle sensor 27 can be prevented with the aforementioned simple structure.

Furthermore, since the operation of the fly wheel 12 may be prevented by the end lock preventive mechanism 44, an end lock due to the fly wheel 12 and/or the vehicle sensor can be prevented. Therefore, an end lock when the seat belt 4 is fully or nearly fully wound may be further prevented.

Additionally, the end lock preventive mechanism 44 may be included with the pair of stoppers 45, 46. The rotation of the eccentric gear 14 controls the pair of stoppers 45, 46, thereby preventing the actuation of the fly wheel 12 when the seat belt 4 is fully or nearly fully wound. Therefore, the actuation of the fly wheel 12 can be prevented by a simple structure.

Furthermore, the end lock preventive mechanism 44 may include the ring portion 12 b on the fly wheel 12 and the pair of stoppers 45, 46 for preventing the actuation of the fly wheel 12. Therefore, a conventional webbing sensor can be employed without significant design change. Additionally, the end lock preventive mechanism 44 may be of simple construction, since the structure must simply press the ring portion 12 b by the stoppers 45, 46.

According to the seat belt unit 1 of this embodiment, the seat belt retractor 3 may be employed. Therefore, end locks due to the vehicle sensor 27 and/or the fly wheel 12 can be effectively prevented, thereby improving the operability of the seat belt 4 and providing smooth and stable operation of the seat belt 4 by the occupant.

According to an exemplary embodiment the end lock preventive mechanism 44 for may be provided with a pair of stoppers 45, 46 and the pair of the guide grooves 47, 48. However, it should be noted that the present disclosure is not limited to this embodiment. For example, according to another embodiment two or more stoppers for pressing the ring portion 12 b and two or more guide grooves for guiding the stoppers may be included. In this case, the respective stoppers and the respective guide grooves may be formed at any of a plurality of positions in the circumferential direction of the eccentric gear 14.

Additionally, as shown in FIG. 14, the pair of stoppers 45, 46 may be adapted to press in outward radial directions α, β of the eccentric gear 14 using an elastic biasing member 53. Accordingly, the ring portion 12 b of the fly wheel 12 can be locked by greater force. In this case, the pair of stoppers 45, 46 and the elastic biasing member 53 may be integrally formed from a resin or a metal. Alternatively, the pair of stoppers 45, 46 and the elastic biasing member 53 may be formed separately and the pair of stoppers may be connected by the elastic biasing member 53.

The aforementioned embodiments are illustrative examples for carrying out the seat belt retractor 3 of the present disclosure. As such, the respective components of the seat belt retractor 3 may be varied within the scope of claims of the present disclosure.

The seat belt retractor and the seat belt unit of the present disclosure may be suitably used as a seat belt retractor such that an end lock due to a vehicle sensor and/or a webbing sensor may occur. The seat belt unit may include at least an emergency locking function and an automatic locking function. Additionally, the seat belt unit may employ the seat belt retractor for restraining an occupant with a seat belt withdrawn from the seat belt retractor.

The priority application, Japanese Patent Application No. 2007-229005, filed Sep. 4, 2007 including the specification, drawings, claims and abstract, is incorporated herein by reference in its entirety.

Given the disclosure of the application, one versed in the art would appreciate that there may be other embodiments and modifications within the scope and spirit of the application. Accordingly, all modifications attainable by one versed in the art from the present disclosure within the scope and spirit of the present application are to be included as further embodiments of the present application. The scope of the present application is to be defined as set forth in the following claims. 

1. A seat belt retractor, comprising: a spool that is rotatably supported by a frame to wind up a seat belt; an emergency locking mechanism for detecting a vehicle deceleration larger than a predetermined threshold, preventing the spool from rotating in a belt withdrawal direction, the emergency locking mechanism comprising: at least one locking mechanism allowing rotation of the spool when the emergency locking mechanism is not in operation and preventing the rotation of the spool in the belt withdrawal direction when the emergency locking mechanism is in operation; a lock gear comprising ratchet teeth on an outer periphery of the emergency locking mechanism and arranged in an annular shape, the lock gear rotating together with the spool when the emergency locking mechanism is not in operation and actuating the locking mechanism when the emergency locking mechanism is in operation creating a relative rotation between the lock gear and spool; and a vehicle sensor comprising an engaging claw and detecting a vehicle deceleration larger than the predetermined deceleration in the event of an emergency, the vehicle sensor actuated to engage the engaging claw with one of the ratchet teeth of the lock gear to prevent rotation of the lock gear in the belt withdrawal direction, creating a relative rotation between the spool and the lock gear; and a first end lock preventive mechanism for preventing the engaging claw of the vehicle sensor from engaging with one of the ratchet teeth of the lock gear when the seat belt is fully or nearly fully wound by the spool, the first end lock preventive mechanism comprising: an end lock preventive member disposed on the frame and set at a locking position where the end lock preventive member does not allow the engaging claw of the vehicle sensor to be engaged with one of the ratchet teeth of the lock gear when the seat belt is fully or nearly fully wound and is set at a non-locking position where the end lock preventive member allows the engaging claw of the vehicle sensor to be engaged with one of the ratchet teeth of the lock gear other than when the seat belt is fully or nearly fully wound; and a control element that sets the end lock preventive member at the locking position when the seat belt is fully or nearly fully wound and sets the end lock preventive member at the non-locking position when the seat belt is not fully or nearly fully wound.
 2. The seat belt retractor as claimed in claim 1, further comprising an automatic locking mechanism that is actuated when the seat belt is fully withdrawn and prevents the withdrawal of the seat belt by winding the seat belt after the seat belt is fully withdrawn until a certain amount of the seat belt is wound, and a lock switching mechanism for switching an emergency locking function mode in which an emergency locking function by the emergency locking mechanism is exercised and an automatic locking function mode such that an automatic locking function by the automatic locking mechanism is exercised, wherein the control element is disposed on a control member of the lock switching mechanism.
 3. The seat belt retractor as claimed in claim 2, wherein the lock switching mechanism comprises a switching lever that is selectively set at either of an emergency locking position where the emergency locking function mode is set or an automatic locking position where the automatic locking function mode is set, and an eccentric gear that rotates when the spool rotates and at a speed lower than the rotation speed of the spool and that has switching lever control cam member for switching the setting position of the switching lever, wherein the control member of the lock switching mechanism is composed of the eccentric gear and the end lock preventive member is composed of an end lock preventive lever that is selectively set at either of the locking position or the un-locking position, and wherein the control element is an end lock preventive member control cam for switching the setting position of the end lock preventive lever.
 4. A seat belt retractor as claimed in claim 3, further comprising a webbing sensor that is pivotally disposed on the lock gear and that detects a withdrawal acceleration larger than normal withdrawal acceleration for wearing the belt when the seat belt is rapidly withdrawn and is thus actuated to prevent the rotation of the lock gear in the belt withdrawing direction so as to create a relative rotation between the spool and the lock gear, and a second end lock preventive mechanism for preventing the actuation of the webbing sensor when the seat belt is fully or nearly fully wound.
 5. A seat belt retractor as claimed in claim 4, wherein the second end lock preventive mechanism has an actuation preventive member that is controlled its actuation by the eccentric gear and prevents the actuation of the webbing sensor when the belt is fully or nearly fully wound.
 6. A seat belt retractor as claimed in claim 5, wherein the second end lock preventive mechanism further includes a ring member disposed on the webbing sensor, and wherein said actuation preventive member is a stopper that presses the ring member to prevent the actuation of the webbing sensor when the seat belt is fully or nearly fully wound.
 7. A seat belt retractor as claimed in claim 6, wherein the stopper is provided with a stopper biasing means for biasing the stopper in such a direction that the stopper presses the ring member.
 8. A seat belt apparatus comprising: a seat belt for restraining an occupant; a seat belt retractor for winding up the seat belt while allowing the withdrawal of the seat belt, the seat belt retractor actuated in the event of an emergency to prevent the withdrawal of the seat belt; wherein the retractor includes a spool that is rotatably supported by a frame to wind up the seat belt and an emergency locking mechanism for detecting a vehicle deceleration larger than a predetermined threshold, preventing the spool from rotating in a belt withdrawal direction, the emergency locking mechanism comprising: at least one locking mechanism allowing rotation of the spool when the emergency locking mechanism is not in operation and preventing the rotation of the spool in the belt withdrawal direction when the emergency locking mechanism is in operation; and a lock gear comprising ratchet teeth on an outer periphery of the emergency locking mechanism and arranged in an annular shape, the lock gear rotating together with the spool when the emergency locking mechanism is not in operation and actuating the locking mechanism when the emergency locking mechanism is in operation creating a relative rotation between the lock gear and spool; and a vehicle sensor including an engaging claw and detecting a vehicle deceleration larger than the predetermined deceleration in the event of an emergency, the vehicle sensor actuated to engage the engaging claw with one of the ratchet teeth of the lock gear to prevent rotation of the lock gear in the belt withdrawal direction, creating a relative rotation between the spool and the lock gear; and a first end lock preventive mechanism for preventing the engaging claw of the vehicle sensor from engaging with one of the ratchet teeth of the lock gear when the seat belt is fully or nearly fully wound by the spool, the first end lock preventive mechanism comprising: an end lock preventive member disposed on the frame and set at a locking position where the end lock preventive member does not allow the engaging claw of the vehicle sensor to be engaged with one of the ratchet teeth of the lock gear when the seat belt is fully or nearly fully wound and is set at a non-locking position where the end lock preventive member allows the engaging claw of the vehicle sensor to be engaged with one of the ratchet teeth of the lock gear other than when the seat belt is fully or nearly fully wound; and a control element that sets the end lock preventive member at the locking position when the seat belt is fully or nearly fully wound and sets the end lock preventive member at the non-locking position when the seat belt is not fully or nearly fully wound. a tongue slidably supported by the seat belt; and a buckle that is fixed to a vehicle floor or a vehicle seat and to which the tongue can be detachably latched. 